Air Duct alternatives - KZ305

Used to own an 81 KZ650 that I sold off a number of years ago and now recently bought a kz305 (1981) recently that I know runs/drives but needs to be gone through. I realize this topic is repeated ad nauseum but curious if there is an alternative to the air box ducts that the bike used stock. This was a same issue I ran into on the 650 in that the air ducts are no longer manufactured in any capacity.

My solution then on the 650 since Z1 enterprises was selling new ducts for the older 650 was to Frankenstein the two air boxes together. Essentially cutting the front off the 70s air box to the front of the 81 box and allowing use of the new air ducts on the 81 air box. Unfortunately the 305 was made in less years and doesn't seem to have an air box/duct combo still manufactured or that I can do this same method. 

So my primary question is, is there anything I'm missing or something people are doing to use the old ducts? I'm familiar with all the old tricks including wintergreen oil, silicone grease/oil, etc. and they never quite worked for me. Also tried the radiator hose tricks and never got it quite right. Hoping there's another part number used for a similar duct or something people can share with me here. I did see the 3d printed version idea but wasn't enough info to go on - I do have a printer for PLA but not sure where to go with that if any.

Thanks for any help in advance and glad to have a KZ back in the stable.

check kawasaki.com or partzilla to see what other models used the same ducts. then search ebaayy. partzilla has an x-ref but go ahead and check other models that are the same/similar size from the 80s. in case there's an oversite in their info. not uncommon nowadays. not that it will necessarily help you but regarding the 650csr: the later ducts fit the airbox and can be adapted at the carburetors using radiator hose to make up the difference. plus some ss band clamps instead of the stock spring bands.  other alternative is to use the later ducts with the bs32 carburetors that came on the 82-83 models. so no futzing around w fitting the ducts.

Hi, another place to try is Cruzin Image, show for 400 and 440, or maybe some of the 4cyl would work, has listings for other manufacturers also, you can probably contact for info,also, used them for bs32’s on 81 650, in Japan and ships real quick good luck

Thanks for the comments.

So as I was concerned, I checked the bike yesterday and sure enough the fittings are soft "enough" to be serviceable for now. I'll keep an eye out for something that will work for the 305. I did cross reference the part # and seems it doesn't equate to any other bikes or part # on a first glance, but will continue my research.

Regarding the air ducts / radiator hosing donuts, I did get that to partially work on the 650 several years ago. Martin_CSR was the one in fact that had put together the suggestion for me iirc. The airbox mod I made was still the best method IMO with a permanent seal, and I personally never got the donuts to work quite right.

Went into my local bike shop for some fuel lines. Had them check for the air ducts out of curiosity. They didn't have any but located one on the Kawi parts inventory in a random Michigan dealer. Called them up and sure enough the part was real and were able to ship it out. Might be the last nos k305 air duct in a dealer in the US!